A variety of analytical techniques are used to characterize interactions between molecules, particularly in the context of assays directed to the detection and interaction of biomolecules. For example, antibody-antigen interactions are of fundamental importance in many fields, including biology, immunology and pharmacology. In this context, many analytical techniques involve binding of a “ligand”, such as an antibody, to a solid support, followed by contacting the ligand with an “analyte”, such as an antigen. Following contact of the ligand and analyte, some characteristic is measured which is indicative of the interaction, such as the ability of the ligand to bind the analyte.
Analytical sensor systems that can monitor such molecular interactions in real time are gaining increasing interest. These systems are often based on optical biosensors and usually referred to as interaction analysis sensors or biospecific interaction analysis sensors. A representative biosensor system is the Biacore® instrumentation sold by GE Healthcare Life Sciences, which uses surface plasmon resonance (SPR) for detecting interactions between molecules in a sample and molecular structures immobilized on a sensing surface. With the Biacore® systems it is possible to determine in real time without the use of labeling not only the presence and concentration of a particular molecule in a sample, but also additional interaction parameters such as, for instance, the association rate and dissociation rate constants for the molecular interaction. The apparatus and theoretical background are fully described in the literature (see e.g., Jonsson, U., et al., BioTechniques 11: 620-627 (1991)). Essentially, the technique involves the immobilization of a ligand to the special surface of a sensor chip, contacting the sensor chip with a flow of sample containing the analyte of interest, and then measuring the change in the surface optical characteristics of the sensor chip arising from the binding of interest. For further details on SPR, reference is also made to U.S. Pat. Nos. 5,313,264; 5,573,956 and 5,641,640.
The integrated microfluidic cartridge (IFC) is a key part in the Biacore instruments. The current IFC is costly to produce and the moulds needed are time consuming to make. Because of the thickness of the injection moulded plates, dead volume of via-holes are rather big. U.S. Pat. No. 6,698,454 describes a new valve design for an IFC with a minimum of silicone rubber (or other elastomer) moulding, compared to the IFC on the market with in silicone rubber flow channels and valves. However, an IFC incorporating such a design has not been introduced onto the market.
Laminated foil microfluidic channels/reactors are available from Takasago Electric, Japan. These are combined with micro-solenoid valves as complete microfluidic devices. Method of making laminated microfluidic structures have also been described before. Various adhesives and strong organic solvents have been used for laminating together polymeric material. US20080178987A1 describes a method that used weak organic material (e.g., acetonitrile) instead of strong organic solvents or adhesives to laminate. U.S. Pat. No. 5,932,799 describes adhesiveless bonding of polyimide films for the generation of microfluidic modules. There, a flexible polymer layer is bonded to the microchannel layers to serve as valves. An exemplary valve layer is given as composed of DuPont's Kapton® KJ thermoplastic polyimide film, with a preferred thickness of about 1 mil.
There is a need, for a valve and associated IFC which is cheaper to make and yet have better performance than the current offerings.